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JustAPI

LLM Serving API

When the inference feature is enabled, JustAPI exposes an OpenAI-compatible API for LLM serving.

Enabling Inference

Section titled “Enabling Inference”
Terminal window
# Build with inference support
cargo build --release --features inference


# Run with a model
justapi serve --model my-model.gguf

Chat Completions

Section titled “Chat Completions”
POST /v1/chat/completions
Content-Type: application/json


{
  "model": "my-model",
  "messages": [
    {"role": "system", "content": "You are a helpful assistant."},
    {"role": "user", "content": "What is Rust?"}
  ],
  "temperature": 0.7,
  "max_tokens": 256,
  "stream": false
}

Response

Section titled “Response”
{
  "id": "chatcmpl-123",
  "object": "chat.completion",
  "created": 1721827200,
  "model": "my-model",
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": "Rust is a systems programming language..."
      },
      "finish_reason": "stop"
    }
  ],
  "usage": {
    "prompt_tokens": 24,
    "completion_tokens": 58,
    "total_tokens": 82
  }
}

Streaming

Section titled “Streaming”
POST /v1/chat/completions
Content-Type: application/json


{
  "model": "my-model",
  "messages": [{"role": "user", "content": "Count to 5."}],
  "stream": true
}

Streaming response (SSE):

data: {"id":"chatcmpl-123","object":"chat.completion.chunk","choices":[{"index":0,"delta":{"role":"assistant"},"finish_reason":null}]}


data: {"id":"chatcmpl-123","object":"chat.completion.chunk","choices":[{"index":0,"delta":{"content":"1"},"finish_reason":null}]}


data: {"id":"chatcmpl-123","object":"chat.completion.chunk","choices":[{"index":0,"delta":{"content":"2"},"finish_reason":null}]}


data: [DONE]

Completions

Section titled “Completions”
POST /v1/completions
Content-Type: application/json


{
  "model": "my-model",
  "prompt": "Once upon a time,",
  "max_tokens": 100,
  "temperature": 0.8
}

Embeddings

Section titled “Embeddings”
POST /v1/embeddings
Content-Type: application/json


{
  "model": "my-model",
  "input": "The quick brown fox jumps over the lazy dog"
}

Model Management

Section titled “Model Management”
GET /v1/models
{
  "object": "list",
  "data": [
    {
      "id": "my-model",
      "object": "model",
      "created": 1721827200,
      "owned_by": "justapi"
    }
  ]
}

Sampling Parameters

Section titled “Sampling Parameters”
Parameter Type Default Description
temperature float 1.0 Sampling temperature
top_p float 1.0 Nucleus sampling threshold
top_k int 40 Top-k sampling
max_tokens int 256 Maximum tokens to generate
stop list[str] [] Stop sequences
presence_penalty float 0.0 Penalize new tokens
frequency_penalty float 0.0 Penalize frequent tokens

See Also

Section titled “See Also”